Galvanometers are often used to rotate mirrors to direct light beams to desired positions. Such arrangements are used, for example, to record information on light-sensitive surfaces. In the application of interest here, the mirrors are used to position light beams on data tracks of optical disk drives and a magneto-optical disk system using a galvanometer-rotated mirror is described in the co-pending U.S. Pat. application of Lee, et. al., entitled Optical Storage System identified as U.S. Patent and Trademark Office Ser. No. 07/847,116.
In the latter system the galvanometer is connected in a servo-loop that receives a command to move the mirror to a desired angular position. A position sensor provides a signal which indicates the mirror position and this signal is compared with the desired position to provide an error signal that drives the galvanometer to the latter position.